1. Field of the Invention
The present invention relates to radio frequency identification (RFID) interrogators and transponders, and more particularly, to a novel communication architecture for an RFID interrogator system.
2. Description of Related Art
In the automatic data identification industry, the use of RFID transponders (also known as RFID tags) has grown in prominence as a way to track data regarding an object to which the RFID transponder is affixed. An RFID transponder generally includes a semiconductor memory in which digital information may be stored, such as an electrically erasable, programmable read-only memory (EEPROMs) or similar electronic memory device. One technique for communicating with an RFID transponder is referred to as “backscatter modulation,” in which the RFID transponder transmits stored data by modulating its antenna matching impedance in order to reflect varying amounts of an electromagnetic field provided by an RFID interrogator. The RFID transponders can therefore operate independently of the frequency of the energizing field, and as a result, the interrogator may operate at multiple frequencies so as to avoid radio frequency (RF) interference, such as utilizing frequency hopping spread spectrum modulation techniques. The RFID transponders may either extract power from the electromagnetic field provided by the interrogator, or may include their own internal power source (e.g., battery).
A drawback of RFID systems is that the backscatter-modulated signal reflected by the RFID transponder may contain relatively low power and limited dynamic range. Therefore, it is important for the RFID interrogator to minimize the noise in both the transmitted and received signal paths in order to achieve an acceptable read range and error rate of the received data. Variation in the tolerances of the electrical components within the RFID interrogator further tends to limit the accuracy of RF and DC parameters of the interrogator operation, thereby increasing susceptibility to noise in the signal paths. It is known in the art for radio designers to strive to create an architecture that minimizes the effect of the parameter variation, but in practice the desired tolerances are nevertheless exceeded.
Accordingly, it would be very desirable to provide an RFID interrogator having a receiver/transmitter architecture that accounts for the variation in tolerances of radio system electrical components.